// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/compiler/backend/x64/unwinding-info-writer-x64.h"
#include "src/compiler/backend/instruction.h"

namespace v8 {
namespace internal {
    namespace compiler {

        void UnwindingInfoWriter::BeginInstructionBlock(int pc_offset,
            const InstructionBlock* block)
        {
            if (!enabled())
                return;

            block_will_exit_ = false;

            DCHECK_LT(block->rpo_number().ToInt(),
                static_cast<int>(block_initial_states_.size()));
            const BlockInitialState* initial_state = block_initial_states_[block->rpo_number().ToInt()];
            if (!initial_state)
                return;
            if (initial_state->register_ != eh_frame_writer_.base_register() && initial_state->offset_ != eh_frame_writer_.base_offset()) {
                eh_frame_writer_.AdvanceLocation(pc_offset);
                eh_frame_writer_.SetBaseAddressRegisterAndOffset(initial_state->register_,
                    initial_state->offset_);
            } else if (initial_state->register_ != eh_frame_writer_.base_register()) {
                eh_frame_writer_.AdvanceLocation(pc_offset);
                eh_frame_writer_.SetBaseAddressRegister(initial_state->register_);
            } else if (initial_state->offset_ != eh_frame_writer_.base_offset()) {
                eh_frame_writer_.AdvanceLocation(pc_offset);
                eh_frame_writer_.SetBaseAddressOffset(initial_state->offset_);
            }

            tracking_fp_ = initial_state->tracking_fp_;
        }

        void UnwindingInfoWriter::EndInstructionBlock(const InstructionBlock* block)
        {
            if (!enabled() || block_will_exit_)
                return;

            for (const RpoNumber& successor : block->successors()) {
                int successor_index = successor.ToInt();
                DCHECK_LT(successor_index, static_cast<int>(block_initial_states_.size()));
                const BlockInitialState* existing_state = block_initial_states_[successor_index];
                // If we already had an entry for this BB, check that the values are the
                // same we are trying to insert.
                if (existing_state) {
                    DCHECK(existing_state->register_ == eh_frame_writer_.base_register());
                    DCHECK_EQ(existing_state->offset_, eh_frame_writer_.base_offset());
                    DCHECK_EQ(existing_state->tracking_fp_, tracking_fp_);
                } else {
                    block_initial_states_[successor_index] = new (zone_)
                        BlockInitialState(eh_frame_writer_.base_register(),
                            eh_frame_writer_.base_offset(), tracking_fp_);
                }
            }
        }

        void UnwindingInfoWriter::MarkFrameConstructed(int pc_base)
        {
            if (!enabled())
                return;

            // push rbp
            eh_frame_writer_.AdvanceLocation(pc_base + 1);
            eh_frame_writer_.IncreaseBaseAddressOffset(kInt64Size);
            // <base address> points at the bottom of the current frame on x64 and
            // <base register> is rsp, which points to the top of the frame by definition.
            // Thus, the distance between <base address> and the top is -<base offset>.
            int top_of_stack = -eh_frame_writer_.base_offset();
            eh_frame_writer_.RecordRegisterSavedToStack(rbp, top_of_stack);

            // mov rbp, rsp
            eh_frame_writer_.AdvanceLocation(pc_base + 4);
            eh_frame_writer_.SetBaseAddressRegister(rbp);

            tracking_fp_ = true;
        }

        void UnwindingInfoWriter::MarkFrameDeconstructed(int pc_base)
        {
            if (!enabled())
                return;

            // mov rsp, rbp
            eh_frame_writer_.AdvanceLocation(pc_base + 3);
            eh_frame_writer_.SetBaseAddressRegister(rsp);

            // pop rbp
            eh_frame_writer_.AdvanceLocation(pc_base + 4);
            eh_frame_writer_.IncreaseBaseAddressOffset(-kInt64Size);

            tracking_fp_ = false;
        }

    } // namespace compiler
} // namespace internal
} // namespace v8
